Battery systems may be used to provide power in a wide variety of applications. Exemplary transportation applications include hybrid electric vehicles (HEV), electric vehicles (EV), heavy duty vehicles (HDV) and vehicles with 42-volt electrical systems. Exemplary stationary applications include backup power for telecommunications systems, uninterruptible power supplies (UPS), and distributed power generation applications.
Examples of the types of batteries that are used include nickel metal hydride (NiMH) batteries, lead-acid batteries, and other types of batteries. A battery system may include a plurality of battery subpacks that are connected in series and/or in parallel. The battery subpacks may include a plurality of batteries that are connected in parallel and/or in series.
Inherent properties of a battery include an ohmic resistance Ro. The ohmic resistance Ro can be modeled as a resistance in series with the battery and estimated based on battery voltage and current measurements. The estimated ohmic resistance Ro can be used to estimate other battery parameters such as state of charge, maximum power, and so forth. There remains a need for methods of estimating the ohmic resistance Ro in situ.